NEW YORK—Beyonce calls the making of her upcoming HBO documentary "Life is But a Dream" a therapeutic process.

She tells the March issue of Vogue, "this movie healed me in so many ways" and thinking about it makes her "want to cry."

The film addresses topics that the notoriously private singer normally doesn't address in public. It chronicles her 2011 decision to no longer have her father Matthew Knowles as her manager, her miscarriage and even the rumors that she was faking her pregnancy with daughter Blue Ivy by really using a surrogate.